The Principal Investigator has shown that platinum drug resistance can be studied in cancer patients actively receiving chemotherapy. This project has been initiated to follow previously reported scientific leads into the mechanisms of platinum drug resistance in patients undergoing therapy. This project differs from the usual laboratory investigations in that the focus is drug resistance in the cancer patient. "Total man-years" above are estimated based on the following: the PI began independent work in November, 1987 after lab renovations were completed; the laboratory technician started on January 4, 1988; and the Biotech Fellow started on July 1, 1988. 1. Cisplatin-DNA adduct can be measured in tissues of human cancer patients after therapeutic levels of drug exposure. Studies have been published by the PI to show that in ovarian and testicular cancer patients, adduct levels in leukocyte DNA correlates with disease response in both diseases, and that adduct levels in bone marrow closely approximate adduct levels in tumor tissues when specimens are obtained at autopsy. Studies are in progress to determine if disease response can be predicted in a prospective manner, based on the first two cycles of chemotherapy.